Tryptophan-derived
indole compounds have been widely investigated as
antioxidants and as
free-radical scavengers. Indole-3-propionic
acid (IPA), one of these compounds, is a deamination product of
tryptophan. In the present study, we used Mongolian gerbils to investigate IPA's
neuroprotective effects against ischemic damage and its antioxidative effects in the hippocampal CA1 region (CA1) after 5 min of transient forebrain
ischemia. The repeated
oral administration of IPA (10 mg/kg) for 15 days before ischemic surgery protected neurons from ischemic damage. In this group, the percentage of
cresyl violet-positive neurons in the CA1 was 56.8% compared with that in the
sham group. In the vehicle-treated group,
glial fibrillary acidic protein (GFAP)-, S-100-, and
vimentin-immunoreactive astrocytes and ionized
calcium-binding adapter molecule 1 (Iba-1)- and
isolectin B4 (IB4)-immunoreactive microglia were activated 4 days after
ischemia/reperfusion, whereas in the IPA-treated ischemic group, GFAP, S-100, Iba-1, and IB4, but not
vimentin, immunoreactivity was distinctly lower than that in the vehicle-treated ischemic groups. The administration of IPA significantly decreased the level of
4-hydroxy-2-nonenal, a marker of lipid peroxidation, in ischemic hippocampal homogenates compared with that in the vehicle-treated ischemic groups at various times after
ischemia/reperfusion. In addition, immunostaining for
8-hydroxy-2'-deoxyguanosine showed DNA damage in pyramidal neurons in the ischemic CA1 was significantly lower in the IPA-treated ischemic groups than in the vehicle-treated ischemic groups. These results suggest that IPA protects neurons from
ischemia-induced neuronal damage by reducing DNA damage and lipid peroxidation.